Fluorescent whitening agents



United States Patent 2,720,523 LUQBESQENT WHIIENWQAGEPJ S I IerbertAugust Lubs, Westmoreland, and Mario Francesco sartori, Monroe Park,Del., assignors to E. I. (In Pout de Nemours & Company, Wilmington,Del., a corporation of Delaware N9 Drsir n r tin atl nlr l ld 25,3,SBHIQINO, 35 F552?" lhisisrsn isaselates th .pras ust qn 9f aws $9 2 1swisha sm t s l as c 9N9?! .t the shave e er l net W is by vb ea a tns arib so el.

Add. ap a n, I at; 2 w ii ,g brigh in tszstilsfihe rid paperis ofrelatively recent developnient. I hasbe en found that fibrous materialswhich normally have a dull, yellowish cast when in the white, unbleachedstate, become whiter and brighter if treated; with agents whichfluoresce under ultraviolet light. Presumably the action of theultraviolet rays present in ordinary daylight is suflicient to eigcitethese agents upon the fiber to emit fluorescence which overcomes theundesirable tinge of color in -the unbleached fiber Best results areobtained when the shade of fluorescence is complementary to that fof theunbleachedffiber,softhat the colors will c'ancel-out each other. Sincethe mpst common ofi-white shade of pnbleached ce llulpsic and mostdesirable shade in a fluorescent is blue.

Another very important demand developed 'by the trade is bleachfastness, inasmuch as the aforementioned fluorescent agents aregenerally incorporated into soap t-andrsynthetic detergents which'arepackaged and marketned-for=household use,and inasmuch as in household.prac miceuilaunderedl-articlesareoften subjected to bleaching rwithtvanious: agents, for instance hy-poch-lorites; it isessenitialuthat tthe fluorescent transferred frorntthe detergent towtheifiberishall not :be removed ortdestroyedby the .action of bleach.Unfortunately, .most of \therfluorescent agents ,lnowsonsthemarket, andhaving t the desirable blueshade, aarer-tweaklzin respect ;to "thisqualification of :bleach resistonce. r i in additiondtoithesabovetwo-primary qualifications, an Lagent:tforxtheipurzposes .of :thisinvention .should be capable of rbeingt-syn'thesized economical-1y fromreadily available materials, and should "have sufficient fluorescentpowei' .(often Preferred l to as itinctorialstrength) to give lithedesired effect at a minimum cost. -Itishould also have affinity tforcellulose ortnylon eflher and-should betcapable ..of Jibeing dissolvedor readily dispersed in: ,water in the "concentrations that wouldnormally betused .in the treatmenttof t the respective fibers. Nowaccording "to our invention inewtchemical compounds are synthesizedwhich satisfy to an excellent deg ree, -all the aforegoingqualifications. The novel com- -poundsof this invention are aromatic-triazoles which are #pbtained by oxidizing QIthO amino azo dyesobtained by coupling 2-diazobenzothiazple s to naphthylamihes which arefree to couple in'position ortho to tlie amino group. They may bedefined generally the formula nelsfN -NT=WQ -whereimR-is-the 2-C radicalof-a benzothiazole selected ylon fibers is yellowish, the

2,720,528 atented 04 t- 1 955 "ice ' monosulf o and sulfamyl derivativesof any of thesei is a 1,2;naphthalerie radical of the grqllp-l flusisting of naphthal ne and in w rse, di msi flsar s 'i when and alltam 'dsst st m .l ltamy' is used here in a generic sense, to include primarysullfss rl (SQ NHZ i ws m asa k ul l f la s 1W ul x ll by lowe alk l dia s w ria radisal h ms Q-atsms ea Whe e t sl CQIQPQUPQT h s s l a sPar-bear smi e the? ma l 1 th q m free acids or i 11 s r'n O sew 9 1 al11292 mi e ab wee -s l hls sal s uc asfth e kal' met la art- 2 1 1isSalts ,As ,py is of the nsmsnp atyr 9 91 na el se ie 9 2 P 9 the .n s tat ta hgrsili 'q haii .sluhil en subse sms a a l- It m be e e b thegeneral formula i i wherein Xdesignates hydrogen, methyl, methoxy, ethylor ethoxy, and which may be named --2- (-6 X 2- benzothiazolyl)t-2H-naphtho (ll;2)-triazo1es. i

The compounds having lsulfo and car-boxy groups are generallywater-soluble, and may be applied to textile *fibersor paper.fromtanfaqueous bath. Those haviing only ,suliarnyl sirbstituents or nosubstituents at all are of interest as fluorescents for, nylonfiber,.and1 may be applied thereto .frpm aqueous dispersions. of thefinely divided ptoduct or from dispersions made by pouring into @Water asolution of the fluorescent in an vorganic solvent such as theCellosolves (lower monoalkyl ethers of diethylene glycol).

,Our ,noyel compounds, may i be synthesized by diazotizjug6-X-Zfllfiumhenzothiazole (wherein 'X has the rneaning aboye indicated),or a monosulfoor. monosulfia derivative thereof, and coupling the diazocomprnrnci in ,acid medium ,to an amino naphthalene which ma 1.1 2 LQtILbQXY, .1.llf0 or .sulfamyl radicals in the nucleus, ,whichjs adaptedforcoupling inposition ortho to the amino grpup. The last condition:impliestthatlthe amino group ,is located ,in position ;2 while fthel-position i s free; or that 21 =l-,naphthylarnine is employedwhich Millrse als int e -PQ iQ y y tu of a ng h v41 tion blocked due ,to thepresenceof a waterjsolubilizing smut i pos tiqnn o 5- Wher ttheaminowbenzothiazole tselssts s t ee tram s lfp gro p tw sulfo .or t ocarboxy groups may be present in the naphthylarnine comllt i lli- Iheresulting ,orthoarnino azo ,cornpqund is then con- .ye rt e d into ,a:triazole by oxidation in known manner, for i 5rstance by heating in an,eguous'sqlutio n of cupric amtrnonipm sulfate or in an aqueous alkalinesolution of sodium hypochlorite until ,the color of the intermediate.azo ,dyehas essentially disappeared, ,andsthen recovering ,thmprqductina desiredphysical or chemical form, .for

instance ,in the form ,ofian alkali-metal ,or ammonium agents of thisinvention may be purified by crystallization from organic solvents or byhypochlorite treatment of an aqueous slurry of the product.

As suitable Z-amino-benzothiazoles for the aforegoing purpose may bementioned Z-amino-benzothiazole, its 6-methyl, 6-ethyl, 6-methoxy and6-ethoxy derivatives; the monosulfo derivatives of any of these,obtained for instance by sulfonation of same with 20% oleum at roomtemperature; the alkali-metal or ammonium salts of such sulfoderivatives; and the corresponding sulfamyl derivatives.

As coupling components for the intermediate amino azo dyestufis preparedabove may be used 2-naphthylamine; 1-naphthylamine-4-sulfonic acid,2-naphthylamine-6-sulfonic acid, and the various isomers of these; thevarious primary sulfamyl, monoalkyl sulfamyl and dialkyl sulfamylderivatives of lor 2-naphthylamine; 2-amino-naphthalene-3-carboxylicacid; l-aminoand Z-amino-naphthalene-4,S-dicarboxylic acid; the variousl-aminoand 2-amino-naphthalene-disulfonic acids; and the alkali-metal orammonium salts of any of the aforegoing.

The requisite sulfamyl derivatives of lor 2-naphthylamine may beprepared by first acetylating the corresponding naphthylamine withacetic anhydride, to block the amino group; then sulfonating thecompound with chlorosulfonic acid to convert it into a sulfonylchloride. The latter is then treated with the appropriate amine(ammonia, methylamine, ethylamine, dimethylamine, etc.) to obtain thesulfonamide. Finally, hydrolysis with hot hydrochloric acid regeneratesthe amino group and gives the desired sulfonamide compound.

The requisite Bz-sulfamyl derivatives of 2-aminobenzothiazole may beobtained by reacting an aminobenzene sulfonamide and sodium thiocyanatein the presence of bromine and acetic acid, according to the proceduredescribed by H. P. Kaufmann et al. in Arch. Pharm. 279, 195, 202-3(1941).

Without limiting this invention, the following examples are given toillustrate our preferred mode of operation. Parts mentioned are byweight.

Example 1 15.0 parts (0.1 mol) of 2-aminobenzothiazole were dissolved in20 parts of concentrated sulfuric acid and diazotized at to C., with asolution of sodium nitrite in concentrated sulfuric acid. The obtaineddiazo solution was added to a solution of 27 parts (0.11 mol) I ofBroenners acid (2-amino-naphthalene-6-sulfonic acid) sodium salt in 400parts of water, while keeping the temperature at 0 to 5 C. The aciditywas then reduced by the aid of sodium acetate to a weakly acid test onCongo red paper and the mixture was allowed slowly to assume roomtemperature. The mixture was then made alkaline to brilliant yellowpaper by addition of 30% sodium hydroxide solution and the amino azo dyewas salted out with sodium chloride and filtered 0E.

The wet dye cake prepared above was dissolved in water and heated at60-70 C., for 23 hours With an alkaline solution of sodium hypochlorite,into which additional alkaline sodium hypochlorite solution was fed at arate sufficient to maintain a positive test to starchiodide paper. Afterclarification of the solution with charcoal, the product was recoveredby salting out, filtering and drying. It was a cream-colored powder,soluble in water with bright bluish fluorescence. The absorp tionmaximum of this compound in aqueous solution is located at 360millimicrons.

Example 2 16.4 parts (0.1 mol) of 2-amino-6-methyl-benzothiazole werediazotized and coupled to 27 parts of the sodium salt of Broenners acid,and the dye was isolated as in Example 1. The orthoamino azo dye thusobtained was.

' at 365 millimicrons.

4 dissolved in 2000 parts of water at C. A solution of 50 parts ofCUSO4.5H2O in 100 parts of water and 300 parts of concentrated ammonia(28%) was added. The mixture was then heated to reflux for 16 hours andthereafter filtered. The cake was dissolved in boiling water, filteredhot; the filtrate was decolorized with aqueous sodium hypochlorite, andthe product was salted out. It was a cream-colored solid, soluble inwater with bright bluish fluorescence. The absorption maximum of thiscompound in aqueous solution is located at 350 millimicrons.

Similar compounds may also be prepared by coupling diazotized2-amino-6-methyl-benzothiazole to naphthionic acid(1-amino-naphthalene-4-sulfonic acid) or to Laurents acid(1-amino-naphthalene-5-sulfonic acid), and oxidizing the amino azo dyesas above.

' were diazotized and coupled to the sodium salt of amino-R acid(2-amino-naphthalene-3,6-disulfonic acid) as in Example 1. The obtainedortho-amino azo dye was oxidized with cupric sulfate and purified as inExample 2. The final product was a light tan powder very soluble inwater with bluish fluorescence. The absorption maximum of this componentin aqueous solution is located The compound is believed to have theformula Naoas SO3N8 Similar compounds may be also prepared by couplingdiazotized 2-amino-6-methyl-benzothiazole to amino-I acid(Z-amino-naphthalene-5,7-disulfonic acid) or to amino-G acid(2-amino-naphthalene-6,S-disulfonic acid) and oxidizing the amino azodyes as in Example 2.

Example 4 19.5 parts 0.1 mol) of Z-amino-6-ethoxy-benzothiazole weredissolved in an acid solution consisting of 160 parts of water and partsof concentrated sulfuric acid, and diazotized, at 5-l0 C., with asolution of sodium nitrite (0.1 mol) in 50 parts of water. A solution of27 parts (0.11 mol) of Broenners acid sodium salt in 400 parts of waterwas added.

The acidity was reduced by the aid of sodium acetate to a weakly acidtest on Congo red paper and the mixture was allowed slowly to assumeroom temperature. The mixture was then made alkaline to brilliant yellowpaper by addition of 30% sodium hydroxide solution, and the amino azodye was salted out and filtered otf. The wet dye concentrate thusprepared was oxidized as in Example 2. The oxidation mixture wasfiltered, and the cake was suspended in water and heated for 15 min. atC. with an excess of a solution of sodium sulfide in water. Afterfiltration, the product was recovered from the filtrate by salting withsodium chloride. It was a tan powder, soluble in water with brightfluorescence. The absorption spectrum of this compound in aqueoussolution is located at 370 millicrons.

Compounds of similar properties are obtained by. following the sameprocedure as in this example, except for replacing the 27 parts ofBroenners acid sodium salt by an equal weight of (a) the sodium salt ofnaphthionic acid, or (b) the sodium salt of Laurents acid.

Example 5 19.5 parts of (0.1 mol) of 2-amino-6-ethoxy-benzothiazole werediazotized and coupled to the sodium salt of amino-R acid as in Example4. The obtained dye was 1'5 oxidized and purified as in Example endproduct was --a light tan product, soluble inwater fluorescence.

Similar fluorescent compounds. are obtained apply- 'ing the sameprocedure to the amino azo dyes obtained by coupling diazotized2-am'ino-6:ethexygbenkothiazole to amino-J acid orto amino-G acid.

. Examples r t 19.5 parts (0.1 mol) of learning-d ethoxy bennothiazolewere diazoti-zed andcoupled to *27 parts-of-Broenners amide(2-naphthylamine-6- sulfqnamide), as in Example 4. The obtained dye wasoxidized as in Example 2. The reaction mass was filtered and the cakewas slurried in water made acid to Congo red paper with hydrochloricacid. This slurry was heated to 80 90 C. to dissolve an copper salts andfiltered hot. The cake was washed with water until acid-free andcrystallized from Cellosolve (a lower monoalkyl ether of diethyleneglycol). It was a yellow powder, soluble in Cellosolve with bluefluorescence. The absorption maximum of this compound in Cellosolvesolution is located at 365 millimicrons. The product is believed to havethe formula:

S OrNH:

Compounds of similar properties are obtained if theZ-amino-6-ethoxy-benzothiazole named in this example is replaced by anequivalent weight of (a) Z-amino-benzothiazole, or (b)Z-amino-6-methyl-benzothiazole.

When the Broenners amide in the above example is replaced by 14.3 parts(0.1 mol) of Z-amino-naphthalene, one obtains a blue fluorescent agentwhich may be applied to cotton or nylon from a dispersion thereof inaqueous organic solvent or in a hot aqueous bath containing a dispersingagent.

Compounds of similar nature may also be prepared according to the aboveprocedure by diazotizing (c) 2- aminobenzothiazole-6-sulfonamide, (d)2-amino-6'methyl-benzothiazole-S-sulfonamide, or (e) 2-amino-6-ethoxy-S-sulfonamide (obtained respectively from p-anilino-sulfonamide,4-methyl-3-sulfamyl-aniline and 4-ethoxy-3- sulfamyl-aniline, accordingto the Kaufimann et al. procedure above mentioned), coupling toZ-amino-naphthalene or to 2-naphthylamine-6-sulfonamide, and thenoxidizing as in Example 2.

Example 7 NaO;S N

HsC

soma

If the Broenner's acid. salt in the above example is replaced by 14.3parts (0.1 mol) of Z-naphthylamine, a product of similar properties isobtained.

isolatedas'the sodium salts of the sulfonic-acids. 3 By using potassiumhydroxide and potassium salts in lieu of sodium hydroxide and sodiumsalts, throughout, the products may be obtained as potassium sulfonates.Isolation as the free sulfonic acids can be effected by acidification ofthe condensation mass, and the products thus obtained may be reactedwith ammonium hydroxide or any suitable organic or inorganic base, toyield the corresponding salt.

In addition to producing a whitening eifect upon textile material orpaper, our novel compounds may also be used for various other purposeswhere fluorescence or absorption of ultra-violet light is desirable, forinstance to achieve fluorescent effects in costumes or stage settings,to achieve novel effects on photographic paper, as ultraviolet filterswhen impregnated on cellulosic films which are used for wrappingmaterials, etc.

We claim as our invention:

1. A compound of the general formula.

f? N=Q wherein R is the 2--C radical of a benzothiazole selected fromthe group consisting of benzothiazole itself, its 6-methyl, G-methoxy,G-ethyl and 6-ethoxy derivatives, and the monosulfo and sulfamylderivatives of any of these, while Q represents the 1,2-radical of anaphthalene compound of the group consisting of naphthalene, itsmonosulfo, disulfo, monocarboxy, dicarboxy and monosulfamyl derivatives.

2. An aromatic triazole compound of the formula =Q wherein R is the 2-Cradical of 6-ethoxy-benzothiazole, while Q is the 1,2-radical ofnaphthalene-6-sulfonic acid.

3. An aromatic triazole compound of the formula W N=Q wherein R is the2-C radical of G-methyl-benzothiazole, While Q is the 1,2-radical ofnaphthalene-fi-sulfonic acid.

4. An aromatic triazole compound of the formula i i N=Q wherein R is the2-C radical of 6-ethoxy-benzothiazole, while Q is the 1,2-radical ofnaphthalene-4-sulfonic acid.

5. An aromatic triazole compound of the formula I ll =Q wherein R is the2-C radical of fi-ethoxy-benzothiazole, while Q is the 1,2-radical ofnaphthalene-fi-sulfonamide.

6. An aromatic triazole compound of the formula W N= wherein R is the2-C radical of benzothiazole, while Q is the 1,2-radical ofnaphthalene-6-sulfonamide.

7. The process of producing a fluorescence agent for textile fiber,which comprises diazotizing a Z-amino-benzothiazole compound of thegroup consisting of Z-aminobenzothiazole itself, its 6-methyl, methoxy,ethyl and ethoxy substitution derivatives, and the monosulfo andsulfamyl derivatives of any of these, coupling the diazo compound thusformed to an amino-naphthalene which is adapted to couple ortho to theamino group and which is a member of the group consisting ofunsubstituted amino-naphthalenes and amino-naphthalenes bearingsubstituents of the group consisting of sulfo, carboxy and s ulfamyl,and then oxidizing the coupled compound to the corresponding triazole.

8. The process of producing a fluorescence agent for textile fiber,which comprises diazotizing a Z-aminobenzothiazole compound of the groupconsisting of 2- amino-benzothiazole itself, its 6-methy1, methoxy,ethyl and ethoxy substitution derivatives, and the monosulfo andsulfamyl derivatives of any of these, couplingthe diazo compound thusformed to an amino-naphthalene which is adapted to couple ortho to theamino group and which is a member of the group consisting ofunsubstituted amino-naphthalenes and amino-naphthalenes bearingsubstituents of the group consisting of sulfo, carboxy and sulfamyl, andthen oxidizing the coupled compound to the corresponding triazole, theoxidation being effected by heating the compound in an aqueous solutionof ammoniacal cupric sulfate.

No references cited.

1. A COMPOUND OF THE GENERAL FORMULA